This invention relates generally to dynamoelectric machines and more particularly to an improved stator for use in such machines.
One of the problems in the art of dynamoelectric machine design has been to minimize material and to reduce the amount of labor required in the manufacturing of such machines and yet not sacrifice performance. There are certain design restrictions which must be considered when attempting to reduce the amount of material used in the stator for an electric motor. For instance, in the stator assembly, sufficient iron must be used to minimize saturation by magnetic flux during operation. Also a sufficient amount of wire must be used to provide the desired operating characteristics. If the size of wire is reduced in a given motor, and all other things held constant, current density increases and too much heat may be generated. These problems are particularly hard to solve in small size electric motors because of, among other things, their inherent physical limitations and especially as such limitations relate to manufacturing tolerances.
In the past, stators having particular utility as permanent-split capacitor, or resistance-split phase motors -- some with alloy wire auxiliary windings, some with backlash auxiliary winding sections, and some with especially high auxiliary winding current density have been designed. These and other approaches are described in more detail in U.S. Pat. No. 3,774,062 to John H. Johnson and U.S. Pat. No. 3,663,057 to Chester A. Smith and William M. Stoddard, both of which are assigned to the same assignee as the present application.
Extra tooling is often required to make laminations for cores of the same nominal size but that are to be wound to permit their use as motors with different auxiliary winding approaches as mentioned above. Therefore, it would be desirable to provide a fixed design stator lamination or core that could be used with many different i.e., congenerous, auxiliary winding approaches.
In numerous applications, particularly in hermetic motors, a mode of mounting the stator must be considered, such as for example, bolt holes in the stator core. However, such bolt holes represent restrictions to magnetic flux and may result in decreased performance. In small motors bolt holes can cause particularly detrimental flux restrictions. It would be desirable to provide a stator of one design for not only congenerous types of auxiliary winding configurations but also such that different bolt hole patterns may be used, and especially where different patterns would require a different total number of bolt holes.
It is desirable to be able to use less expensive winding material than copper wire, such as aluminum wire, and also to punch laminations for a stator in a manner to minimize the amount of scrap. For instance, in a strip of material wide enough to accommodate one lamination, a lamination having at least two flat sides may be designed to use less material than a round lamination since advantage could be taken of the parallel sides of the strip of material. However, laminations having flatted sides can make solution of other problems mentioned above even more difficult since scarcity of yoke material along the flatted sides may result in less flux carrying capacity.
In view of the foregoing, it should now be understood that it would be desirable to provide a stator that would solve most of the above problems.
Accordingly, one object of the present invention is to provide a motor lamination and/or core structure capable of permanent-split capacitor or capacitor start or capable of resistance-split phase motors using alloy wire auxiliary windings, backlash auxiliary winding sections, or high current density auxiliary windings.
Another object is to provide a stator lamination and/or core for a small size electric motor wherein different mounting hole patterns may be readily provided without necessitating rearrangement and/or sizing of winding accommodating slots.
Yet another object is to provide a stator for a small size electric motor wherein minimum amounts of core material are used and yet wherein at least one of the windings may be of aluminum wire.